1.) If you want to read up on science, check out Dr. Erik Ervin at the University of Delaware (formerly of Virginia Tech). Plenty of it going back 16 or more years with good citations. Here's a good primer:
http://www.aapfco.org/presentations/2015/2015_AN_biostimulant_research.pdf
2.)There's not a problem, necessarily, with mixing your own. What I'll ask though is, if I gave you the parts to make a toaster, could you build it? While I'm not trying to be an ***, I am saying it's how these products are formulated that drive up costs. Which raw materials are used, from which sources, how are they extracted and reacted, how the solution's pH is buffered, are just some of the simple questions to ask yourself.
With that said, there's simply not enough data out there to suggest that seaweed from Nova Scotia, while it has higher growth hormone levels, allows grass to perform better than seaweed from South Africa. Same goes for leonardite from New Mexico or North Dakota that eventually extracted in humic and fulvic acids. Hell, we can even go as far as which peat bog produces better humic substances. The point is, this quickly turns into a Ford/Chevy debate.
3.) The article regarding humics causing pesticide failures, this is a direct result of alkaline hydrolysis in the spray tank. Specifically, most of the humic acid products are derived from reacting leonardite with potassium hydroxide (KOH) which has a high pH. As a result the solution has a high pH which can render many pesticides nearly inert as they are designed to be within a fairly low pH range within the spray tank.
Know what you're doing and what you're tank mixing regardless of which approach you take.
4.) I wrote this on another thread about NEXT products.
There are only four types of products we use on grass:
a.) Products that flat out don't work.
b.) Products that make you feel good about applying but, you don't know if they really work.
c.) Products that you know really work but don't make you feel good (see expensive).
d.) Products that make you feel good about applying because you know they really work (see good value).
Only you can be the judge.
